这个存储过程错在哪里？？

SQL code

CREATE PROCEDURE genid ()
BEGIN 

DECLARE st VARCHAR(100);
  START TRANSACTION;
    
    IF NOT EXISTS (SELECT 1 FROM order_key) THEN
        SET @sqlstr=CONCAT('insert into order_key select substring(`key`,8) from order', DATE_FORMAT(CURDATE(), '%Y%m'), ' order by id desc limit 1');
        PREPARE st FROM @sqlstr;
        EXECUTE st;
    ELSE     
        UPDATE order_key SET id=id+1;
    END IF;
    SELECT id FROM order_key;
    COMMIT;
END

有一个专门生成id的表order_key
初始化的时候是从order201208 就是order+当前月中取key字段的中8个以后的数字 插入表order_key中

order201208
id key data
1 x2012081 ds
2 x2012082 24 
3 x2012083 14

也就是说现在取到的是3 3会被插入到order_key的id字段中。然后被跟新为4

上面的存储过程我执行的时候有问题，苦于找不到问题来求助！

------解决方案--------------------
delimiter //
CREATE PROCEDURE genid ()
BEGIN 

DECLARE st VARCHAR(100);
START TRANSACTION;

IF NOT EXISTS (SELECT 1 FROM order_key) THEN
SET @sqlstr=CONCAT('insert into order_key select substring(`key`,8) from order', DATE_FORMAT(CURDATE(), '%Y%m'), ' order by id desc limit 1');
PREPARE st FROM @sqlstr;
EXECUTE st;
ELSE
UPDATE order_key SET id=id+1;
END IF;
SELECT id FROM order_key;
COMMIT;
END
//
------解决方案--------------------

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引用:

delimiter //
CREATE PROCEDURE genid ()
BEGIN

DECLARE st VARCHAR(100);
START TRANSACTION;

IF NOT EXISTS (SELECT 1 FROM order_key) THEN
SET @sqlstr=CONCAT('insert……